Conventional binary signaling includes sending information by means of two distinguishable states (e.g., 1 and 0). Conventional ways of transferring multi-state information (e.g., information that has more than two distinguishable states) over a single channel (e.g., a single wire plus a return) requires some form of multi-state encoding.
One conventional way to send multi-state information over a single signal channel is to encode the multi-state digital data into packets of bits and send the packets using binary serial signaling.
Another conventional way to send multi-state information over single signal channel is to associate different signal amplitudes with different states. In one example, a “ternary” or “three-state” communication scheme comprises a sending unit to encode a sequence of three distinguishable digital states into a signal comprising three distinct signal amplitudes and a receiving unit that receives and decodes the signal levels to reconstruct the original sequence of digital states. An example of such a system is described in Gruodis et al, U.S. Pat. No. 3,155,845, “Three Level Converter,” issued Nov. 3, 1964.
With reference to FIG. 1, multiphase switching power converters (e.g., multiphase switching power converter 10) may comprise a plurality of switching power converter phases 14a 14b . . . 14n controlled by a digital phase controller 12. As described in U.S. patent application Ser. No. 11/969,659 entitled “Power Supply and Controller Circuits” (hereafter referred to as the “Digital Control Application,” which is assigned to the same assignee as the subject application and which is incorporated in its entirety by reference, a digital phase controller 12 can send both binary switch state information as well as phase enable/disable control information to each phase.
For example, when a phase (e.g., phase 14a, FIG. 1) is enabled by the digital controller 12, the ON and OFF states of a pair of switches in the phase (e.g., switches SPa and SSa, FIG. 1) may be defined by the state of a binary PWM signal sent by the controller: e.g., a power switch (e.g., switch SPa, FIG. 1) is ON and a synchronous switch (e.g., switch SSa, FIG. 1) is OFF when the binary PWM signal is high, and the power switch is OFF and the synchronous switch is ON when the binary PWM signal is low.
When the phase is disabled by the digital controller, however, both the power and phase switches are turned off. Thus, three distinct switch states are possible for the combination of the power switch and the synchronous switch: ON/OFF, OFF/ON, and OFF/OFF.
One way to communicate this information is to use a pair of channels (e.g., one “enable/disable” channel and one switch control channel); another way is to use a three-state signaling scheme over one channel.
An example of a multiphase switching converter using a plurality of three-state channels to connect a digital controller chip to a plurality of power converter phases is shown in data sheet FN9159.6, entitled “ISL6612A, ISL6613A Advanced Synchronous Rectified Buck MOSFET Drivers with Pre-POR OVP,” dated Jul. 27, 2006, published by Intersil Corporation, Milpitas, Calif., USA (the “Intersil Data Sheet”).